Fix #7619: nudge fast planes sooner towards their target #8531
Fixes #7619 (part B).
Motivation / Problem
Fast planes kept overshooting their point for state transition. #7619 has an epic image about it.
For non-NewGRF planes, "count" is never above 1. So planes can
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.
For non-NewGRF planes, "count" is never above 1. So planes can smoothly be guided to their destination. For NewGRF planes, they can go as quick as "count" values of 20. This easily overshoots the target. So, calculate if the plane will overshoot, and start nudging him to the destination earlier. You won't notice this either way, as it all happens within a single tick.